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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Wed, Sep 23, 2026 at 10:24:36AM +0800, Lance Yang wrote: > > mm/khugepaged.c | 32 ++++++++++++++++++++++++++++++-- > > 1 file changed, 30 insertions(+), 2 deletions(-) > > > >diff --git a/mm/khugepaged.c b/mm/khugepaged.c > >index f49a6710933b..dab421f8233e 100644 > >--- a/mm/khugepaged.c > >+++ b/mm/khugepaged.c > >@@ -1278,6 +1278,23 @@ static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_stru > > return SCAN_SUCCEED; > > } > > > >+static pgtable_t alloc_deposit_pte(struct mm_struct *mm) > >+{ > >+ /* > >+ * khugepaged is run from a kernel thread, so need to manually set the > >+ * correct memcg so the allocation gets charged correctly. > >+ */ > >+ struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm); > >+ struct mem_cgroup *old_memcg = set_active_memcg(memcg); > >+ pgtable_t pgtable; > >+ > >+ pgtable = pte_alloc_one(mm); > >+ > >+ set_active_memcg(old_memcg); > >+ mem_cgroup_put(memcg); > >+ return pgtable; > >+} > >+ > > /* > > * collapse_huge_page() expects the mmap_lock to be unlocked before entering and > > * will always return with the lock unlocked, to avoid holding the mmap_lock > >@@ -1293,7 +1310,7 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long s > > LIST_HEAD(compound_pagelist); > > pmd_t *pmd, _pmd; > > pte_t *pte = NULL; > >- pgtable_t pgtable; > >+ pgtable_t pgtable = NULL; > > struct folio *folio; > > spinlock_t *pmd_ptl, *pte_ptl; > > enum scan_result result = SCAN_FAIL; > >@@ -1310,6 +1327,12 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long s > > goto out_nolock; > > } > > > >+ if (is_pmd_order(order)) { > >+ pgtable = alloc_deposit_pte(mm); > >+ if (!pgtable) > >+ goto out_nolock; > > One small thing: result is still SCAN_SUCCEED after alloc_charge_folio(), > > result = alloc_charge_folio(&folio, mm, cc, order); > if (result != SCAN_SUCCEED) > goto out_nolock; > > if (folio_memcg_alloc_deferred(folio)) { > result = SCAN_ALLOC_HUGE_PAGE_FAIL; > goto out_nolock; > } > > if (is_pmd_order(order)) { > pgtable = alloc_deposit_pte(mm); > if (!pgtable) > goto out_nolock; > } > > so if alloc_deposit_pte() fails, collapse_huge_page() returns success > without installing a PMD. > > I see sashiko pointed that out too :) > > Cheers, Lance Sigh ack yeah oops :) I think SCAN_ALLOC_HUGE_PAGE_FAIL is the closest though it's not allocating a huge page so much as the page table, but gets the correct MADV_COLLAPSE -ENOMEM back. (Another case of local AI review not catchign something btw! Sashiko does lean towards over-reporting/hallucinating but catches more) Will ask Andrew to update in reply to this patch as a quick thing rather than respin so quick, and fix up on any respin. -- Cheers, Lorenzo _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv